The invention relates to a magnetic actuator, and in particular to a magnetic actuator applied in a reflecting mirror actuator.
A magnetic actuator drives electronic components by utilizing a magnet surrounded by coils. The magnet provides magnetic field. When an electric current is occurried in the coil, current flow is perpendicular to magnetic field lines of the magnet. According to Ampere's Law, relative motion is produced between the coil and the magnet. Resultant motion produced by the magnetic actuator can be applied in optical devices or other conventional mechanism.
In FIG. 1, a conventional magnetic actuator is shown. The conventional magnetic actuator 1 comprises a hollow cylindrical magnet 10, a coil 12, and a yoke base 14. The magnet 10 can be a permanent magnet with external and internal sides having opposite poles. In this case, the external side has a North pole, and the internal side a South pole. The coil 12 encircles the magnet 10, for electric current to flow therethrough. The yoke base 14 is connected to a side of the magnet 10. The magnetic field line 100 produced by the magnet 10 extends radially from an external edge of the magnet 10, passes through the coil 12, and enters an internal edge of the magnet 10, as shown in FIG. 1. As a result, if electric current flows through the coil 12, the electric current is perpendicular to the magnetic field line. Thus, coil 12 will move therefore axially with respect to the magnet 10 as shown by the arrow in FIG. 1. The magnetic actuator can be installed in a mechanism that requires relative motion between elements.
Another conventional magnetic actuator is shown in FIG. 2A. The magnetic actuator 2 comprises a solid cylindrical magnet 20, a yoke 25, a coil 22, and a yoke base 24. The magnet 29 is also a permanent magnet with an upper end, North pole, and a lower end, South pole. The yoke 25 is located above the magnet 20 and connected thereto. The coil 22 encircles the yoke 25. The yoke base 24 is below the magnet 20. The magnetic field line 200 produced by the magnet 20 emits axially from the upper end thereof, traveling from the yoke 25 through the coil 22 and entering the magnet 20 from the yoke base 24. If electric current flows through the coil 22, current flow is perpendicular to the magnetic field line such that relative axial motion is produced between the coil 22 and the magnet 20.
Another magnetic actuator is shown in FIG. 2B. The difference from the above mentioned is that a side board 26 is connected to the yoke base 24 located below the magnet 20. The side board 26 extends from the yoke base 24 to the coil 22 such that the magnetic field line 200 easily extends along the side board 26 and the yoke base 24, and the magnetic field line 200 passing through the coil 22 can be concentrated, thereby providing improved actuation.
However, the actuation of the conventional magnetic actuators is still deficient. For example, in an optical device for transferring light produced from a light source to a light with predetermined intensity and color, the light is projected to produce images. A reflecting mirror actuator is a main component of the optical device to provide high image resolution. The reflecting mirror actuator is commonly provided with a magnetic actuator to direct and project light in different directions, as shown in FIGS. 3A and 3B. The reflecting mirror actuator 3 comprises a reflecting mirror 31 and a base 32 with a pivot point 33 therebetween. The reflecting mirror 31 can rotate by the pivot point 33 as a center point. A magnetic actuator 30 is disposed at a side of the reflecting mirror 31 and the base 32 to control the movement of the reflecting mirror 31. When the coil of the magnetic actuator 30 has no current therethrough, as shown in FIG. 3A, the light is reflected by the reflecting mirror 31 in a predetermined position. When a current is occurred in the coil of the magnetic actuator 30, as shown in FIG. 3B, the magnetic actuator 30 actuates the reflecting mirror 31 to rotate by the pivot point 33 such that the light reflected by the reflecting mirror 31 changes to another predetermined position. The reflecting mirror actuator is required to operate rapidly such that the light emitting directions can be changed immediately and resolution increased. Thus, actuation of the conventional actuators is often insufficient because of its structure. In order to satisfy demands for high actuation, the actuator must be enlarged, whereby requirements for more compact design cannot be met. If electric current is increased in the coil, there is also a problem of excessive power consumption. Thus, there is still a need to provide a compact magnetic actuator with high actuation without increasing current of a coil without increased size.